GB621593A - Transmitting and receiving circuits for wave transmission systems - Google Patents

Abstract

621,593. Discharge apparatus. WESTERN ELECTRIC CO., Inc. Nov. 15, 1946, No. 33978. Convention date, Jan. 30, 1943. Addition to 575,432. [Class 39 (i)] [Also in Group XL (c)] Terminal apparatus of the type described in the parent Specification for an electric signalling system comprises a coaxial line or wave-guide connecting a transmitter and receiver to a common channel (e.g. an aerial), and a pair of cavity resonators coupled to the coaxial line or wave-guide so as to block the receiver during transmission and the transmitter during reception. Each resonator contains a gas discharge device, the couplings of the resonators to the coaxial line or wave-guide being linearly spaced a distance equal to a small odd multiple of a quarter wavelength (Fig. 6). In an alternative arrangement employing coaxial lines only one resonator associated with the receiver is employed (Fig. 2, not shown). The gas discharge device connector across the resonant chamber associated with the receiver is adapted to discharge in response to the resonant voltage applied to the cavity by the outgoing waves from the transmitter to effectively short-circuit the cavity and thus the input to the receiver, but to remain in the undischarged condition in response to an incoming wave, whilst that associated with the transmitter is adapted to discharge only during incoming waves. The cavity resonator, Fig. 3, comprises an upper rectangular box portion 8 and lower cylindrical portion 9, mounted slidably on a coaxial line 1. The portion 9 has a small slot 11 in one side opposite to and opening into the slot 5 in the outer coaxial conductor 4, so as to provide a window electrically coupling one side of the cavity to the line 1. Tuning of the resonator is effected by means of the slidable portion 13 and screw 12. The receiver coupling 2 is attached directly opposite the slot 11. Connected across the cavity of the portion 9 is a gas discharge tube 15, having electrode 16 and 17 forming the spark-gap, and an auxiliary electrode 18. The electrode 18 is maintained at a fixed negative potential with respect to the electrode 16 and 17 and is employed to reduce the leakage power at the initiation of the firing of the tube. Specification 589,023 and U.S.A. Specification 2,063,342 are referred to.